Associate Professor University of Massachusetts Amherst Amherst, Massachusetts, United States
Objectives: Cancer cachexia is a prominent feature of patients with pancreatic ductal adenocarcinoma (PDAC). Cachexia is characterized by rapid weight loss, and augmented energy expenditure. However, it is controversial whether aberrant brown fat activation and thermogenic energy expenditure is involved in the cachectic weight procedures. Emerging evidence suggests that iron metabolism is altered during pathogenic progression of PDAC. This study aims to investigate the paracrine effects of PDAC on brown fat differentiation and its associated iron metabolism.
Methods: We established an in vitro model utilizing a cell line derived from PDAC KPC mice (KrasG12D;Trp53R172H;Pdx1-Cre) and conditioned-medium (CM) was collected for detecting proinflammatory cytokine levels by ELISA. The murine brown HIB1B preadipocytes were differentiated into lipid laden brown adipocytes in the presence of 5% PDAC conditioned-medium (KPC-CM). The markers of brown adipogenesis, thermogenesis, iron metabolism, and mitochondria biogenesis are measured by qPCR and Western blot analyses. The impact of PDAC media on energy flux is determined by Seahorse XF analyzer.
Results: KPC-CM contained various proinflammatory cytokines and chemokines, including CXCL1, LIX, CCL1, and IL-12. Addition of 5% of KPC-CM significantly reduced HIB1B brown adipocyte differentiation, evidenced by reduced brown signature gene and protein expressions of PPARγ, PRDM16, DIO2 and UCP1. Moreover, KPC-CM was shown to impair mitochondria function by suppressing PGC1α, TFAM, and CRLS1. The deregulation of brown thermogenesis is partly attributed to the deregulated iron metabolism, including failure to activate IRP and reduced transferrin receptor-mediated iron uptake. Supporting this, KPC-CM markedly diminished oxygen consumption rate in HIB1B brown adipocytes.
Conclusions: Taken together, our findings suggest that the brown fat differentiation is significantly attenuated in PDAC patients via dysregulated iron homeostasis. It also implicates that normal brown fat-derived thermogenic function is reduced in PDAC patients.
